Project Description Tuberculosis (TB) remains one of the major causes of global mortality/morbidity, and has become increasingly prevalent and deadly as a result of HIV/AIDS and the emergence of multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB). Global control of TB appears difficult because of the lack of an effective protective vaccine and lack of sterilizing drugs. Since drug resistance is likely to increase, there is a pressed need to develop effective vaccine or immunotherapeutic. We have recently made serial novel observations suggesting that V?2V2 T cells, the dominant ? T-cell subset in humans/primates, play a role in host response and immune regulation, and contribute to anti-microbial immunity against infections including M. tuberculosis (Mtb). Particularly, we elucidate that Mtb phosphoantigen (E)-4- hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP) can associate with APC surface molecule, bind to TCR on V?2V2 T cells, and activate/expand V?2V2 T cells. Importantly, HMBPP plus IL-2 treatment of macaques induces massive expansion of multi-functional V?2V2 T effector cells. HMBPP-expanded V?2V2 T effector cells can traffic to and accumulate in airway/lung, produce anti-TB cytokines IFN?/perforin/granulysin, confer anti-TB immunity after Mtb infection and even induce homeostatic protection against fulminating pneumonic plague lesions in lungs. Based on these findings, we hypothesize that V?2V2 T cells can function as anti-TB effectors, homeostatic mediators and immune regulators enhancing CD4/CD8 T-cell responses, and confer anti-TB immunity in Mtb infection. To test this hypothesis, we will I. Determine mechanisms by which HMBPP-expanded V?2V?2 T effector cells confer anti- TB immunity. II. Determine whether V?2V2 T-cell-targeted treatments during chronic Mtb infection can confer immunotherapeutics against severe TB lesions and/or TB cavities. III. Determine if HMBPP/IL-2 expansion of V?2V2 T cells can overcome depressed responses of CD4/CD8 T cells and protect against HIV-related TB in SHIV-infected macaques with low CD4 counts.